A "slightly different" GVW question

[foobar]

Originally Posted by dznf0g

"Airstream does not specify a TW limit."

If you hunt on the coupler, you will find a max load spec stamped in the steel. On mine it is partially obscured by the jack flange, but it clearly states 1000# max TW load.

Also page B-10 of my owner manual is clear at this link. "...must not exceed 1000 pounds..."

https://www.airstream.com/wp-content...manual-109.pdf

Just read page B-10.

In the 4th paragraph below the image of the trailer and tow vehicle, the manual states that you should “unhitch” from the tow vehicle and then measure the tongue weight.

This means that we unplug the WD hitch from the tow vehicle receiver. It does not mean that we should remove the hitch assembly before measuring the tongue weight. It seems pretty clear that this methodology intends to include the hitch weight at part of the trailer tongue weight limit.

[dznf0g]

Originally Posted by foobar

Just read page B-10.

In the 4th paragraph below the image of the trailer and tow vehicle, the manual states that you should “unhitch” from the tow vehicle and then measure the tongue weight.

This means that we unplug the WD hitch from the tow vehicle receiver. It does not mean that we should remove the hitch assembly before measuring the tongue weight. It seems pretty clear that this methodology intends to include the hitch weight at part of the trailer tongue weight limit.

Yeah, and they also weigh at the jack, which is a 43# difference from coupler weight (at the ball) on my trailer. This is what I mean about a huge ambiguity surrounding the componentry between the receiver and the tongue area. The truck doesn't give a hoot what your weight at the jack is. It's off the ground while underway.

Maybe one can argue that 40# ain't a big deal. Problem is each data point is then used to calculate, through multiplication and division, several times, to calculate other measures (axle loads, weight changes, etc. ) this magnifies any inaccuracies to the point that resulting figures are wildly off.

[foobar]

Originally Posted by dznf0g

Yeah, and they also weigh at the jack, which is a 43# difference from coupler weight (at the ball) on my trailer. This is what I mean about a huge ambiguity surrounding the componentry between the receiver and the tongue area. The truck doesn't give a hoot what your weight at the jack is. It's off the ground while underway.

Maybe one can argue that 40# ain't a big deal. Problem is each data point is then used to calculate, through multiplication and division, several times, to calculate other measures (axle loads, weight changes, etc. ) this magnifies any inaccuracies to the point that resulting figures are wildly off.

As I referred to in one of my longer explanations above, you should determine total tongue weight empirically using a commercial truck scale (this will include the weight of the full WD hitch setup). Here is the method:

Make sure your trailer is fully loaded as it would be when taking it on a trip.

Drive all 4 wheels of your vehicle on the scale while your trailer is still attached and WD bars are NOT tensioned. Record the weight. DO NOT drive your trailer on the scale with your vehicle (I.e. only the tow vehicles wheels are on the scale). You are getting the weight of your vehicle only while under load.

While the vehicle is still on the scale, unhook the trailer and lift the tongue jack high enough so that there is no weight on the hitch ball. Again, be sure that no part of the trailer is on the scale. Record the weight. This is the weight of your tow vehicle.

Subtract the two weights from each other to give you your tongue weight.

[dznf0g]

"I have no idea if airstream (or more likely, the airstream chassis manufacturer) intends for the WD hitch to be included in that value stamped on the trailer tongue metal."

And this is what aggravates me relative to the same term...tongue weight....being used by both manufacturers. I believe the trailer manufacturer intends for TW to be the weight bearing down on the ball. This includes the portion of the total trailer and its contents, plus the portion of the hitch system which is permanently mounted to the a-frame and a portion of those components "suspended" between the a-frame and and the head. The TV manufacturer want TW to be a total of everything inserted into the receiver. The location of each component is determinant to its effect on either TW calculation. It isn't just an additive figure.

[foobar]

Originally Posted by foobar

As I referred to in one of my longer explanations above, you should determine total tongue weight empirically using a commercial truck scale (this will include the weight of the full WD hitch setup). Here is the method:

Make sure your trailer is fully loaded as it would be when taking it on a trip.

Drive all 4 wheels of your vehicle on the scale while your trailer is still attached and WD bars are NOT tensioned. Record the weight. DO NOT drive your trailer on the scale with your vehicle (I.e. only the tow vehicles wheels are on the scale). You are getting the weight of your vehicle only while under load.

While the vehicle is still on the scale, unhook the trailer and lift the tongue jack high enough so that there is no weight on the hitch ball. Again, be sure that no part of the trailer is on the scale. Record the weight. This is the weight of your tow vehicle.

Subtract the two weights from each other to give you your tongue weight.

Commercial CAT scales charge 10-12 dollars for the first weigh, and then 1 - 2 dollars for each additional weight measurement for the next 24 hours.

Using CAT scales is a cheap and easy way to properly dial in your WD hitch and restore the tow vehicle front axle weight to it’s normal value when the trailer is not hitched up. You just make multiple CAT scale weight passes with the tow vehicle and trailer on the weight scales. You adjust the WD bar tension between passes.

[foobar]

Originally Posted by dznf0g

"I have no idea if airstream (or more likely, the airstream chassis manufacturer) intends for the WD hitch to be included in that value stamped on the trailer tongue metal."

And this is what aggravates me relative to the same term...tongue weight....being used by both manufacturers. I believe the trailer manufacturer intends for TW to be the weight bearing down on the ball. This includes the portion of the total trailer and its contents, plus the portion of the hitch system which is permanently mounted to the a-frame and a portion of those components "suspended" between the a-frame and and the head. The TV manufacturer want TW to be a total of everything inserted into the receiver. The location of each component is determinant to its effect on either TW calculation. It isn't just an additive figure.

Agree. I neglected to point out that the position of each load along the lever arm (the trailer tongue plus hitch extension) modulates the load that is placed on the tow vehicle receiver. It was an intentional simplification to try and make the explanation a little easier to follow.

Anyway, all such effects are accounted for in the CAT scale method of empirically determining the tongue weight that I just outlined.

[dznf0g]

Originally Posted by foobar

As I referred to in one of my longer explanations above, you should determine total tongue weight empirically using a commercial truck scale (this will include the weight of the full WD hitch setup). Here is the method:

Make sure your trailer is fully loaded as it would be when taking it on a trip.

Drive all 4 wheels of your vehicle on the scale while your trailer is still attached and WD bars are NOT tensioned. Record the weight. DO NOT drive your trailer on the scale with your vehicle (I.e. only the tow vehicles wheels are on the scale). You are getting the weight of your vehicle only while under load.

While the vehicle is still on the scale, unhook the trailer and lift the tongue jack high enough so that there is no weight on the hitch ball. Again, be sure that no part of the trailer is on the scale. Record the weight. This is the weight of your tow vehicle.

Subtract the two weights from each other to give you your tongue weight.

Oh, you're certainly correct. It all begins and ends with the CAT scales. I use those scales to back into ALL calculations and cross check with sherline and multiple calculations of the ingredients which make up the CAT scale findings.

However CAT scales only tell you resultant "balances" at some given WD setting. For example (and I'm being wildly ridiculous here) those scale readings won't tell you whether your calculated "TW" from the no-WD weigh and the WD weight reflect a coupler weight of 2# with a hitch weight of 998# or a coupler weight of 998# and a hitch weight of 2#. So is your A-frame overloaded or not?

This comes into play for another thread....you know....the one about the front wall of the AS buckling. These weight exercises mean more than just, "what are my axle loads"? There are others as well. Why is my receiver twisting/flexing/cracking?

[dznf0g]

"Using CAT scales is a cheap and easy way to properly dial in your WD hitch and restore the tow vehicle front axle weight to it’s normal value when the trailer is not hitched up."

Ooooh, now you're getting me riled up. Relative to my last post and the numbers you need to know. (hey, if your TV manufacturer says to restore 100% of FA load, then go for it) Most manufactures (by carline) say to either restore 50% of weight or 50% of the distance from ground to fender. If you are applying excessive WD, then you are creating problems (like front wall damage). Time for number crunching and rebalancing all loads. Not saying you, in particular are.

[foobar]

Originally Posted by dznf0g

"Using CAT scales is a cheap and easy way to properly dial in your WD hitch and restore the tow vehicle front axle weight to it’s normal value when the trailer is not hitched up."

Ooooh, now you're getting me riled up. Relative to my last post and the numbers you need to know. (hey, if your TV manufacturer says to restore 100% of FA load, then go for it) Most manufactures (by carline) say to either restore 50% of weight or 50% of the distance from ground to fender. If you are applying excessive WD, then you are creating problems (like front wall damage). Time for number crunching and rebalancing all loads. Not saying you, in particular are.

Fair point. I was speaking in general. In all cases, you should follow the tow vehicles recommendation for how much WD tension should be applied. This is usuallly specified to be measured by either how much front axle vehicle suspension deflection is reduced (I.e. how much to reduce the change in front wheel well height) or how much of the front axle weight to restore when measured on a CAT scale. Basically, what I’m saying is to read the d*mn manual for the tow vehicle and follow the instructions :-)

[dznf0g]

Originally Posted by foobar

Fair point. I was speaking in general. In all cases, you should follow the tow vehicles recommendation for how much WD tension should be applied. This is usuallly specified to be measured by either how much front axle vehicle suspension deflection is reduced (I.e. how much to reduce the change in front wheel well height) or how much of the front axle weight to restore when measured on a CAT scale. Basically, what I’m saying is to read the d*mn manual for the tow vehicle and follow the instructions :-)

Agreed, but I would add, read all the manuals and look for the specs for all the weight bearing components in the total system. It is entirely possible, especially with 2500s or 3500s, to be under on trailer axle, tv rear axle and front axle loads, while being horribly out of balance and overloading some component.

This theory of, "buy a big truck, load everything and forget about it" is dangerous....if only to the equipment, if you're not careful.

[SYC2Vette]

Originally Posted by foobar

Just read page B-10.

In the 4th paragraph below the image of the trailer and tow vehicle, the manual states that you should “unhitch” from the tow vehicle and then measure the tongue weight.

This means that we unplug the WD hitch from the tow vehicle receiver. It does not mean that we should remove the hitch assembly before measuring the tongue weight. It seems pretty clear that this methodology intends to include the hitch weight at part of the trailer tongue weight limit.

From etrailer website (I read the same thing on a FAQ on a WD mfg website but can't find it now, will keep searching). I am not defending this position, and hopefully won't get anybody too "riled up", but no wonder some folks are confused by this!

Expert Reply:
The Blue Ox TrackPro Weight Distribution w/ Sway Control part # BLU67FR weighs in at about 90 lbs. all told. With that said it should not be added to the tongue weight when picking a WDH for your trailer. The design is such that it comes out to balance or zero weight when installed.

[dznf0g]

Originally Posted by SYC2Vette

From etrailer website (I read the same thing on a FAQ on a WD mfg website but can't find it now, will keep searching). I am not defending this position, and hopefully won't get anybody too "riled up", but no wonder some folks are confused by this!

Expert Reply:
The Blue Ox TrackPro Weight Distribution w/ Sway Control part # BLU67FR weighs in at about 90 lbs. all told. With that said it should not be added to the tongue weight when picking a WDH for your trailer. The design is such that it comes out to balance or zero weight when installed.

Yeah, a lot of folks can't understand the effect of the trailer being moved rearward and the relationship that has on the corresponding "receiver weight". I do question if it is actually zeroed out. I'd have to have some actual weights and measures to calculate it. My gut tells me it would be near zero, unless the drawbar has a longer shaft....of course that introduces other undesirable characteristics. Potentially.

[Dennis C]

This is an interesting thread. I never really thought about the weight of the WDH as anything other than additional payload weight for my truck, but I can see the logic in the assertion that it should be trailer payload or zeroed out. As pointed out earlier in this thread, it ultimately doesn’t make much difference. My Blue Ox Sway Pro weighs just under 70 lbs. I’ve run the 3-pass weight calculation at the CAT scales more than once. I have a pretty good idea how well my rig is balanced and I know that it’s well within my limits. I think the challenge for many people here is that they want a simple formula with limited variables that will tell them that their setup is safe. Unfortunately there are many variables and it’s not always as simple as people would like.

[dznf0g]

Originally Posted by Dennis C

This is an interesting thread. I never really thought about the weight of the WDH as anything other than additional payload weight for my truck, but I can see the logic in the assertion that it should be trailer payload or zeroed out. As pointed out earlier in this thread, it ultimately doesn’t make much difference. My Blue Ox Sway Pro weighs just under 70 lbs. I’ve run the 3-pass weight calculation at the CAT scales more than once. I have a pretty good idea how well my rig is balanced and I know that it’s well within my limits. I think the challenge for many people here is that they want a simple formula with limited variables that will tell them that their setup is safe. Unfortunately there are many variables and it’s not always as simple as people would like.

I agree in that, if you have plenty of headroom in your TV and AS capacities, and you're loading in a proper and balanced manner, it may matter little to explore beyond the CAT scale results.

There is a pretty wide variation in all of the "business" going on between the receiver mouth and the rear of the tongue area, while being within specs for your particular rig capacities. IMO, it becomes extremely important when determining things like spring bar capacity selection, deciding where you really need to be relative to the TW percentage range, diagnosing root cause of things like front wall buckling and cracking, etc.

It most definitely is NOT as simple as people would like.

[JCWDCW]

Originally Posted by Bill M.

Gross wt is total of axles and tongue. I see no reason to count hitch weight in the trailer gross wt. The hitch becomes part of the TV. The pivot point is the ball. Maybe something different with a Hensley. I have no experience there.

The Hensley is definitely on the Tongue of the trailer but once hooked up it is distributed to the TV and Trailer suspension. One of the downsides to the Hensley style is how much it weighs. Few people can lift the whole assembly and carry it.
That being said, the Hensley is fully supported by the TV, since you always have to crank up the equalizer jacks to "lift" the rear of the TV.


Perhaps the question is whether the max weight limit of the trailer, fully loaded, is to protect the frame and running gear of the trailer. Weight on the tongue from the hitch parts attached to the frame is weight on the frame. Equalizing stresses the A frame and the TV Receiver, both so additional weight up front although distributed, is still a stress on the frames of both vehicles.
JCW

[SYC2Vette]

Well I heard back from Blue Ox, and they confirmed what etrailer said that the 80-90 lbs of the weight distribution components (what you see in a photo of a WD system on the website) does NOT add to tongue weight. I have plenty of margin on tongue weight anyway so I guess the CAT scale results are all I care about. Still a bit of a puzzlement.

[dznf0g]

Originally Posted by SYC2Vette

Well I heard back from Blue Ox, and they confirmed what etrailer said that the 80-90 lbs of the weight distribution components (what you see in a photo of a WD system on the website) does NOT add to tongue weight. I have plenty of margin on tongue weight anyway so I guess the CAT scale results are all I care about. Still a bit of a puzzlement.

Did you ask them what they are calling tw? Coupler weight or receiver weight? Is suspect receiver weight.

Sent from my SM-G950U using Airstream Forums mobile app

[PaulinVA]

Entertaining esoteric discussion. Now, how many angels fit on the head of a pin?

[Ndcctrucks]

Originally Posted by dznf0g

The guy at E-Trailer is correct....for a WD hitched system.....not for one who is "towing on the ball" (sans WD).

When you apply WD force, you create a trussed beam system running from the receiver mouth (or pin) to the trailer axle(s). It's no different than a truss bridge for a roadway.

The math is a bit more complicated than just adding the weight of all the hitch components to the trailer weight to arrive at GVW, but it's reasonably close enough.

Nicely-put👍

[SYC2Vette]

Originally Posted by dznf0g

Yeah, a lot of folks can't understand the effect of the trailer being moved rearward and the relationship that has on the corresponding "receiver weight". I do question if it is actually zeroed out. I'd have to have some actual weights and measures to calculate it. My gut tells me it would be near zero, unless the drawbar has a longer shaft....of course that introduces other undesirable characteristics. Potentially.

Yeah, I think I get it now. Using the simplistic notion of the wheelbarrow, if I waddle up to the TV and attach the WD system, and lift up, the very first thing that happens prior to transferring any other loads is that the weight of the WD system is offloaded from the TV hitch to the arms, so therefore it is obviously part of the trailer GVW not the TV at that point. Any further "lifting of the arms" performs the load transfer of the tongue weight.